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I installed a Willwood big front brake kit ( six piston calipers ) up front and 2002 Z28 brakes on the rear with a Willwood master cylinder and adjustable proportioning valve.
my car was a front disk power brake car from the factory.
I am still using my stock brake booster and was wondering if anyone knows if I could change my booster to get more out of my brakes ? If so what size booster would be ideal ?
The car is stopping and I would not have the booster on my mind except for the fact when I back out of my drive way ( slightly down hill ) I really have to push the Pedel hard to stop car. I have adjusted rear brake bias on the proportioning valve but no real difference.
under normal driving the car seems to stop ok, but I only have a couple of hundred miles on car since the restoration and I haven’t really put the braking system under any real stress yet.
It may just be that I am not used to older cars, but with the braking system that is on this car I feel that it should be performing better.
So, how did the brakes work before the swap? I have a couple of newer cars with excellent 4 wheel disc Brembo brakes and when I get into the Cutlass I am not disappointed with the factory front disc/rear drum braking capabilities. Sounds as though something on your car is not working properly,and I doubt it is the booster unless you have a faulty one.
Let’s back up. How much vacuum do you have at idle? What is the piston area of your current front and rear calipers? What pad compound are you running? What size master cylinder bore? Does the master have an adjustable length rod? What hole did you use on the brake pedal with the booster?
You need to provide current system specifications before anyone can really give accurate advise.
Update: I forgot to ask what booster you are using. Are you using a stock 11" single diaphragm booster? A dual diaphragm booster? If a dual, what size?
Last edited by 70Rocket; April 30th, 2020 at 07:45 AM.
Let’s back up. How much vacuum do you have at idle? What is the piston area of your current front and rear calipers? What pad compound are you running? What size master cylinder bore? Does the master have an adjustable length rod? What hole did you use on the brake pedal with the booster?
You need to provide current system specifications before anyone can really give accurate advise.
Update: I forgot to ask what booster you are using. Are you using a stock 11" single diaphragm booster? A dual diaphragm booster? If a dual, what size?
six piston calipers up front still trying to figure out piston area
11” stock booster
I will need to check my vacuum again I check it before but don’t don’t remember PSI I do remember thinking I had enough.
master cylinder piston bore 1”
piston stroke 1.10”
Hawk pads
SSBC all in one adjustable prop valve / distribution block.
Last edited by rogiestone; May 3rd, 2020 at 07:37 AM.
Reason: Forgot to address caliper piston area
I am wondering if you have a mismatch in your system components. Its not uncommon for new big brake kits to have significantly less piston area for the front calipers compared to the OEM calipers. Unless the rest of the system is designed around the reduced piston area, the calipers will generate less clamping force than the OEM. Most of the Wilwood six piston calipers fall into this area.
If this is the root of your problem, there are a few ways it could be addressed. Let us know what front calipers and the piston area when you get a chance.
Also, I understand you have Hawk pads, but what compound? Hawk makes a ton of different brake compounds for a given pad shape. These compounds have different characteristics. You select the compound based on what best fits your application - i.e. they have different friction levels, initial bite, thermal resistance, cold pad performance, more of less dusting, etcetera. Hawk pad compounds span the range of OEM type replacement pads to sprint and endurance road race pads. After we have a full understanding of your system, one of the easiest ways to increase brake performance may be a change to the pad compound to one that has a higher cold pad friction level. For example, maybe using a HPS or HP Plus compound.
If you are having trouble figuring out the caliper piston area and the Hawk brake compound, post the part numbers for the calipers and the pads. I can probably figure it out from there. If the calipers came it the kit, I might be able to figure it out based on the kit number.
I have not ordered the kit yet, i contacted a company that had a kit on e-bay that said it will work on 14" wheels, will work with my master cylinder, but will need a prop valve. They were going to call me back with their "tech" guy to confirm everything, but must have got busy. Maybe I will hear from them on Fri.
Not sure if this is allowed, so if not please delete.
I need to let other fellow members know about a bad experience I have had with the company Johnny Law Motors.
I contacted the company about a front disc brake conversion kit. I had a few questions about fitment for my vehicle so they put me in contact with their "tech guy". He answered the questions I had, so I went ahead and ordered the kit he told me would fit.
It was well in excess of $400, and when I received the kit there were no calipers, or brake pads in the kit.
I called customer service and was ran around to multiple "departments". The "tech guy" told me he would make it right, but when he put me back to customer service, and they in turn told me the kit I ordered did not include the calipers or pads. There was a kit that I could have ordered that included the calipers, but they were much more. I tried my best to keep my cool & ask them why in the world would I order a drum to disc brake "conversion" kit & not need the two most important parts to the kit. They in turn basically told me that I was SOL, but I could buy the calipers from them. To put it nicely on here I told them to pound sand. (Just not in those words).
I just wanted to warn anyone else that was planning on doing a conversion kit on their vehicle, do not go through them.
Thank You for letting me vent........sorry if this is not allowed.
April 29th, 2020, 04:36 PM
